Kuwait's emir says military action by four Arab countries blockading Qatar has been averted as Trump changes his tone.

The emir of Kuwait says the threat of war between Qatar and Arab nations blockading it for the past three months has been neutralised.

Sheikh Sabah Al Ahmad Al Sabah, the main mediator in the Gulf dispute, spoke in Washington, DC, on Thursday at a joint press conference with US President Donald Trump.

While both sides in the dispute have ruled out the use of armed force, some ordinary Qataris say they worry about the possibility of military action, given the ferocity of the criticism their country has received from media in the four Arab states.

"What is important is that we have stopped any military action," Sheikh Sabah said.

In a joint statement, the blockading nations expressed regret about the Kuwaiti emir's comment about stopping military intervention.

"The military option was not and will not be [used] in any circumstance," it said.

Saudi Arabia, the United Arab Emirates, Egypt and Bahrain cut diplomatic and trade links with Qatar on June 5, suspending air and shipping routes with the world's biggest exporter of liquefied natural gas. Qatar is also home to the region's biggest US military base.

The countries reiterated on Thursday the accusation that Qatar continued to finance "terrorism" and interfere in the internal affairs of other countries.

Trump said there is still funding of radical groups by some nations, but added multiple countries are responsible. "There is massive funding of terrorism by certain countries," he said.

The joint statement by the blockading nations praised what they called Trump's firm assertion that the only way to resolve the crisis was by stopping the support and financing of "terrorism", "and his unwillingness to resolve the crisis unless this is achieved".

Sheikh Sabah said he had received a letter from Qatar that expressed willingness to discuss a list of 13 demands from its neighbours.

"We know that not all of these 13 demands are acceptable," Kuwait's leader said, referring specifically to issues that affected Qatari sovereignty. "A great part of them will be resolved."

Qatari Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani said that any mediation had to come "without conditions", reiterating Doha would not negotiate while transport links with neighbours remained cut.

The Arab powers responded in the statement by accusing Qatar of putting preconditions on negotiations, which they said showed a lack of seriousness in resolving the dispute.

Qatari officials have repeatedly said the demands are so draconian they suspect the four countries never seriously intended to negotiate them, and were instead seeking to hobble Doha's sovereignty.

At the same time, they have said Qatar is interested in negotiating a fair solution to "any legitimate issues" of concern to fellow Gulf Cooperation Council member states.